The major objectives of the present study are to characterize lymphocyte subpopulations involved at different sites in the immune response to bladder cancer at different stages in tumor development in an animal model. Using the chemical carcinogen N-(4-(5-nitro-2-furyl)-2-thiazolyl)formamide (FANFT) to induce the production of bladder tumors in rats, lymphocytes are harvested at different stages of tumor development, purified and then tested functionally against a variety of cell lines and characterized morphologically for surface characteristics. These tests are as follows: (1) immunofluorescent labelling for T and Ig surface markers; (2) testing of spontaneous and antibody-dependent lymphocyte cytotoxicity using a 51Chromium-release assay with a variety of tumor target cell lines; (3) testing of lymphocyte responsiveness in a mixed lymphocyte/tumor cell culture system in which subsequent lymphocyte incorporation of 3H-Thymidine into DNA is examined and subsequent cytotoxicity against. 51Chromium-labelled target cells is assessed. Finally, because previous work in our laboratory has demonstrated a possible participation of cyclic AMP in the modulation of the immune response to bladder cancer, role of this substance in interactions between lymphocyte populations and tumor target cells during the development of an immune response to bladder cancer in this model is being assessed.